Fiber optic sensor utilizing broadband sources

Abstract

Fiber optic sensors employ a high brightness light source such as a fiber optic supercontinuum source, multiplexed superluminescent light emitting diodes, or a broadband tunable laser diode. Light is delivered to the measurement location via fiber optics and sensor optics directs infrared radiation onto material the being monitored that is located in a hostile environment. A disperse element is positioned in the detection beam path in order to separate the wavelengths and to perform spectral analysis. A spectral analysis of the radiation that emerges from the sheet yields information on a plurality of parameters for the material. For papermaking applications, the moisture level, temperature and cellulose content in the paper can be obtained.

1. A sensor system configured to direct illuminating light onto a composition so as: to produce detection radiation along a detection beam path for measuring a plurality of parameters in a composition that comprises:
 a high brightness light source; 
 means for generating detection radiation from the high brightness light source wherein the detection radiation has predetermined wavelength ranges to detect a plurality of parameters in the composition; 
 a fiber optic radiation delivery system that delivers the detection radiation to an optical head comprising first optics operable to direct the detection radiation to the composition and second optics operable to direct light that emerges from the composition to a fiber optic radiation retrieval system; 
 a detector operable to receive and measure light from the fiber optic radiation retrieval system; 
 a dispersive element that is disposed in the detection beam path; and 
 means for analyzing the light from the fiber optic radiation retrieval system to calculate the plurality of parameters of the composition. 
 
     
     
       2. The sensor system of  claim 1  wherein the high brightness light source comprises a fiber supercontinuum source. 
     
     
       3. The sensor system of  claim 2  wherein the dispersive element comprises a tunable bandpass filter or a grating spectrometer. 
     
     
       4. The sensor system of  claim 2  wherein the detector comprises a detector array and the dispersive element comprises a grating spectrometer or a linear variable filter. 
     
     
       5. The sensor system of  claim 1  wherein the high brightness light source comprises a plurality of superluminescent light-emitting diodes and an optical multiplexer having (i) an input that is configured to receive light from the plurality of superluminescent light-emitting diodes and (ii) a plurality of outputs that are configured to deliver light to the fiber optic radiation delivery system. 
     
     
       6. The sensor system of  claim 5  wherein the dispersive element comprises a tunable bandpass filter or a grating spectrometer. 
     
     
       7. The sensor system of  claim 5  wherein the detector comprises a detector array and the dispersive element comprises a grating spectrometer or a linear variable filter. 
     
     
       8. The sensor system of  claim 1  wherein the high brightness light source comprises a tunable laser diode. 
     
     
       9. The sensor system of  claim 8  wherein the detector comprises a single element photodiode. 
     
     
       10. The sensor system of  claim 1  wherein the composition comprises paper and the means for analyzing the light from the second fiber optic radiation delivery system calculates the temperature, cellulose content and water content of the paper. 
     
     
       11. The sensor system of  claim 1  wherein the fiber optic radiation delivery system comprises one or more first optical fibers that are routed through a first take-up mechanism and the fiber optic radiation retrieval system comprises one or more second optical fibers that are routed through a second take-up mechanism. 
     
     
       12. A method of performing measurements with a sensor that detects a plurality of parameters in a composition that comprises the steps of:
 providing a high brightness light source that is located remotely from the composition; 
 providing an optical head comprising a first optics that directs radiation to the composition and a second optics that collects radiation that emerges from the composition; 
 providing a fiber optic radiation delivery system for directing radiation from the high brightness light source to the first optics; 
 providing a fiber optic radiation retrieval system for receiving radiation that is directed from the second optics and for transmitting the radiation to a radiation detector, wherein the high brightness light source generates illuminating radiation of sufficient optical power density to produce detection radiation along a detection beam path to the radiation detector; 
 positioning a dispersive element in the detection beam path; and 
 analyzing the light from the fiber optic radiation retrieval system to calculate the plurality of parameters of the composition. 
 
     
     
       13. The method of  claim 12  wherein the high brightness light source comprises a fiber supercontinuum source. 
     
     
       14. The method of  claim 13  wherein the dispersive element comprises a tunable bandpass filter or a grating spectrometer. 
     
     
       15. The method of  claim 13  wherein the detector comprises a detector array and the dispersive element comprises a grating spectrometer or a linear variable filter. 
     
     
       16. The method of  claim 12  wherein the high brightness light source comprises a plurality of superluminescent light-emitting diodes and an optical multiplexer having (i) an input that is configured to receive light from the plurality of superluminescent light-emitting diodes and (ii) a plurality of outputs that are configured to deliver light to the fiber optic radiation delivery system. 
     
     
       17. The method of  claim 16  wherein the dispersive element comprises a tunable bandpass filter or a grating spectrometer. 
     
     
       18. The method of  claim 16  wherein the detector comprises a detector array and the dispersive element comprises a grating spectrometer or a linear variable filter. 
     
     
       19. The method of  claim 12  wherein the high brightness light source comprises a tunable laser diode. 
     
     
       20. The method of  claim 19  wherein the detector comprises a single element photodiode. 
     
     
       21. The method of  claim 12  wherein the fiber optic radiation delivery system comprises one or more first optical fibers that are routed through a first take-up mechanism and the fiber optic radiation retrieval system comprises one or more second optical fibers that are routed through a second take-up mechanism. 
     
     
       22. The method of  claim 21  wherein the fiber optic radiation delivery system and the fiber optic radiation retrieval system are routed through a take-up mechanism along coextensive paths. 
     
     
       23. The method of  claim 12  wherein the composition comprises paper and the plurality of parameters include moisture content, temperature, and cellulose content.